Light emission and deterioration in epoxy resin subjected to power frequency electric fields

Light emission from an epoxy resin specimen with pin-plane electrodes was studied using a refrigerated 13-stage photomultiplier and a 4-stage image intensifier. In the pretreeing period weak light, comparable in intensity to that resulting from thermal photomultiplier noise, was observed together with visible effects of deterioration such as fine shadow lines and void formation and growth. The deterioration in the void-free state is probably caused by hot electron bombardment of resin molecules in the high field region.